A U.S. soldier serving in Afghanistan has been captured and is believed to be in militant custody, according to U.S. officials in Kabul.
The soldier was apparently captured by Taliban forces in eastern Afghanistan Tuesday, though none of the militant groups operating in the area have claimed responsibility for the capture.
Officials also tell ABC News that all available assets are being used to find and locate the soldier, whose family has been notified of his situation.
The Pentagon has withheld his name from the public, not wanting to reveal information that could aid the insurgents who are holding him.
The captured soldier is a young infantryman who was stationed at a remote outpost in Paktika Province, which is along the border with South Waziristan, a hilly region in northwest Pakistan.
He was discovered missing when his bulletproof body armor and rifle were found at the base.
The military has not been in direct contact with his captors, but he is presumed to have been captured because of intercepted Taliban communications indicating he is under the group's control.
He is believed to be the first American soldier captured in Afghanistan.
Few details about the circumstances of his capture have been released officials say, to protect the soldier's safety, including whether anyone else was with him. It would be "highly unusual" that the soldier would be alone off base in Afghanistan, says ABC News' Martha Raddatz.
An Afghan police official told The Associated Press the soldier went missing in the Mullakheil area of eastern Paktika province during the day Tuesday. There is an American base in the region, the official said.
Taliban spokespersons in Afghanistan Qari Yousif Ahmadi and Zabiullah Mujahid both told ABC News they had no information on the whereabouts of the soldier. A number of insurgent organizations operate in eastern Afghanistan, including the Taliban.
This is the first U.S. military person captured since June 2006, when two soldiers were taken and then slaughtered south of Baghdad.
4,000 Marines Involved in Helmand Offensive
The news comes the same week U.S. Marines launched a major anti-Taliban military offensive in southern Afghanistan. The missing soldier was reportedly not part of that operation.
Paktika, where the soldier went missing, is a stronghold for Siraj Haqqani, one of the primary threats to U.S. forces in eastern Afghanistan. Haqqani is also the person believed to have held New York Times reporter David Rohde.
It's likely that the soldier would be taken across the border into South Waziristan in order to get him to an area where U.S. troops do not officially operate. The Taliban have reportedly told their forces that if they capture any foreign national they should transfer him to Waziristan in order to avoid being caught by U.S. planes.
South Waziristan is also the next target of the Pakistani military and where Baitullah Mehsud's network is based.
The current offensive "Khanjar" (or "Strike of the Sword") against the Taliban in south Afghanistan is the first major operation under President Barack Obama. It was launched today in Helmand province, and involves nearly 4,000 U.S. Marines as well as 650 Afghan soldiers.
The stated goal of the operation is to crack down on insurgency in Helmand -- the world's largest opium poppy producing region -- before Afghanistan holds presidential elections on August 20.
ABC News' Aleem Agha in Kabul contributed to this report.